1. Field of the Invention
The invention relates to vehicular wheel chock clamps for rim mounted pneumatic tires and, more specifically, to a clamp that may be readily interlocked with a tire, per se, to prevent rotation of an inflated tire relative to the clamp. This is effected by a controlled compression of a discrete area or areas in one or both tire sidewalls to the extent that the compressing element or elements may be fully embedded in the tire to, in effect, act as a fixed rack tooth with respect to the uncompressed tire wall areas on either side thereof which uncompressed side wall areas act, in effect, as adjacent pinion teeth.
The necessary tire wall compression to interlock a clamp and tire, as described above, may be determined empirically. For example, a loaded boat trailer of approximately 2,500 pounds gross weight with a cold tire inflation pressure of 50 P.S.I. was fitted with a wheel chock clamp, of the type herein disclosed, sized to impinge the trailer undercarriage upon forced rotation of the wheel and chock clamp. A single compressing element 1" wide and 3/8" thick fully embedded (i.e. 3/8") into one of the tire sidewalls effected a positive interlock with the tire. Thus when the wheel was initially chocked against forward motion and the trailer forcibly pulled forward, the wheel and interlocked chock clamp rotated as a unit for approximately 120 degrees as the chock was rolled over and came into abutting engagement with the trailer undercarriage at which time the interlocked tire skidded along the pavement as forced towing was continued.
2. Prior Art Statement
There are prior art wheel chock clamps that interlock with a wheel rim, as opposed to the tire, to preclude rotation of the wheel relative to the clamp as by a clamp extension passing laterally through an opening in the rim itself, as for example, in U.S. Pat. No. 4,833,442. The disadvantage in this type wheel interlock is that virtually all wheel rims are different, many do not have suitable lateral openings and others employ hub caps that cover whatever openings there may be. The prior art has generally recognized the practical shortcomings of this type interlock and has opted for telescoping chock clamps, laterally adjustable to accommodate various rim/tire widths, with lateral extensions that overlie the rim thus precluding removal of the clamp radially of the tire. Exemplary are U.S. Pat. Nos. 4,768,359; 5,134,868; 5,372,018 and International Publication Number WO 86/05150. While the latter mentioned exemplars may indeed preclude removal of the chock clamps they offer little resistance to a thief intent upon stealing a vehicle with the clamp still in place. This is so because the "locked" wheels can rotate relative to, and within the locked confines of, the wheel clamp.
U.S. Pat. No. 5,372,018, although bearing a superficial resemblance to the present invention, does not prevent theft of the trailer since the "lock" disclosed therein is not, and cannot be, rotationally interlocked with the wheel or any part thereof. Thus a thief simply tows the trailer forwardly over the "lock" which is then dragged behind the wheel as the wheel rotates relative to the trailing "lock". The same is true for the "lock" disclosed in IPN WO 86/05150.
Similarly, a locking device such as shown in U.S. Pat. 5,134,868 which "firmly" engages opposite sides of a solid, smooth surfaced wheel rim (column 3, lines 10-12 and lines 21-23) via a pair of blunt ended metal jaws is nothing more than that "finger tight" engagement with the rim as may be effected by an output force equal only to the input force (1:1) of the individual applying the lock. The blunt metal to metal engagement of the jaws and solid, smooth rim as may be effected by a 1:1 force application could obviously not resist even manual rotation of the locking device relative to the wheel through the mechanically advantaged intermediary of the extended chock legs. Even more obvious is the fact that said "firm" engagement will yield upon impingement of the chock with a vehicle undercarriage.
More specifically if the locking device of U.S. Pat. No. 5,134,868 is positioned to chock rearward movement of the vehicle then as the vehicle is moved forwardly the "finger tight" engagement may or may not be sufficiently tight to lift the weight of the lock but if it is, as soon as the chocking elements impinge the vehicle undercarriage, the "finger tight" engagement will yield and the vehicle tire will rotate relative thereto as the vehicle is moved forwardly. If the locking device is positioned to chock forward movement, a thief need only jack up the vehicle and rotate the wheel until the lock is in a trailing position with the same result as described above. If a thief does not have a jack to rotate the wheel until the lock is in a trailing position, he need only pull or pry the extended chock legs upwardly until they are parallel to the ground, or he can move the vehicle rearwardly a few inches until the chock legs are similarly raised at which time a line is looped around the ratchet bar and secured to a convenient undercarriage element after which the vehicle may be moved forwardly with the chock legs well clear of the ground and the rim clamping jaws sliding readily along the rim.
In the case of U.S. Pat. No. 4,768,359, a thief need only roll the vehicle rearwardly over the lock to position the same forwardly of the wheel and spaced above the ground, whereafter a straightened coat hanger or other line is passed through the lock shackle and secured to the front bumper or any convenient undercarriage element and the car may be driven off with the rim embracing bars sliding along the rim lip.
Clamp type locks employing teeth to penetrate the tire as in U.S. Pat. No. 5,247,815 disclose no tire compression and are otherwise undesirable in that the vehicle owner who forgets the clamp is in place will ruin his tire.